PROJECT SUMMARY/ABSTRACT Providing evidence-based treatment to pregnant women with opioid use disorder (OUD) is essential to fighting the opioid epidemic. Many people with OUD spend time in jails, and they are eventually released back into the community. Jails thus also represent an important part of the strategy to address the opioid epidemic, by providing treatment to incarcerated people with OUD and creating community linkages for post-release treatment. This is especially true for pregnant women with OUD, as opioid withdrawal should be avoided due to maternal and fetal risks, and they should receive medication assisted treatment (MAT). However, treatment of pregnant people with OUD in jails is variable and many women are forced to detox. The reasons for this gap in care for pregnant women in jail are multifactorial, and relate to the unique organizational, logistical, and cultural environment of providing care in a correctional setting. Strategies to implement evidence based MAT for pregnant women in jails are urgently needed. In order to advance the goal of disseminating and implementing treatment for pregnant women with OUD and thereby advancing individual and public health goals, three aims will be undertaken: (1) to examine perceived barriers and attitudes about MAT for pregnant women with OUD in jail from key jail administrative and clinical stakeholders and from community treatment providers using a mixed methods approach with surveys and qualitative interviews; 2) to collect qualitative data from pregnant women with OUD in jail on their perceived barriers and attitudes about receiving MAT in jail and upon release; 3)to design and pilot a jail-specific, patient- centered implementation strategy that incorporates jail stakeholder and patient perspectives to provide MAT to pregnant women with OUD in jail. My career goal is to be a leader in patient-oriented research focused on improving quality of care and outcomes for pregnant women with OUD in the criminal justice system. To support me in meeting my career goals, I have assembled a mentorship team of senior investigators in different research disciplines, who have a track record of successful research collaborations and mentoring activities. I have also designed a complementary didactic and experiential training plan to acquire knowledge and skills in implementation science, treatment of OUD in pregnancy, and addiction policy research. The proposed career development plan contains the training, mentoring, and resources to become a successful independent investigator.